Safety stop for balancers



April 27, 1937. F. P. FORSS SAFETY STOP FOR` BALANCERS Filed Jan. 2, 1956 mmlmuum@ Q I INVENTOR. Fmr/#0F [D Fofnsy ATTORNEY.

Patented Apr. 27, 1937 UNITEDl STATES .PATENT oFFlcE SAFETY STOP FOR'YBALANCERS' Application January 2, 1936, "Serial-No. 57,318

Claims.

This invention relates to balancers and more particularly to spring balancers for suspending portable power operated tools, such as electric drills,.reamers, polishers,-and the like, from over- 5 .head supports.

A balancer of the character referred to has a revoluble drum or reel on which winds a cable, the outer end of which is outside of the drum housing for connection with the tool or load to bev raised and lowered by the drum. A spiral spring, preferably within the drum, turns the drum in a direction to raise the load on the cable. The spring is tensioned to counter-balance the weight of the tool attached to the cable so that the tool may be raised and lowered and be handled in a lowered position without requiring the operator to support the weight of the tool. The inner end of the cable is fixed to the drum so that the cable will wind on the drum and retain its connection with the drum when paid out to its fullest extent.

The object of my invention is to provide a safety lock to automatically stop the rotation o-f the drum before the inner end of the cable reaches the cable outlet opening in the balancer casing and thus avoid straining or injuring the connection between the cable and the drum when the cable is paid out to its fullest extent.

A further object of my invention is to control the operation of the safety lock by the cable, the

lock being normally held inoperative by the cable when wound on the drum, but released for action when the cable is unwound from vthe drum to the extent above noted.

One embodiment of my invention is disclosed in the accompanying specification and drawing,

in which:

Fig. 1 is a vertical sectional view with parts in elevation of a spring balancer embodying Vthe safety lock of my invention, the section being taken on line I-I of Fig. 2;

Fig. `2 is an elevational view with parts broken away and in section, respectively, of the balancer showing the safety lock and the inner end of the cable attached to the drum; and

Fig. 3 is a sectional view taken on line 3--3 of Fig. 2 to show the abutment or shoulder for the to the section 3 by one or more cap screws 5 asv :,shown.

'I'he drum is preferably of the tapered type and is provided with a spiral groove 6 to receive Aa cable 1. inner end 8 secured to theA larger end o-f the drum as at 9. The connection is of the character de- 'Ihe cable, as shown -in Fig. 2., has-itsl sirecl and anchors the cable end to a web I0 in the.drumxconstruction The outer end of the cable is outside of the drum casing, the cable-passing outof the casing through a cable outlet open.l ing 3a provided inthe lowerv portion 4of the sec-r. 5 tion 3.

A spiral spring I I turns the drum in a direction to Wind the cable onthe drum. This spring has. its outerlend secured to the drum in any preferred manner and its innerend I2 is secured to a sleeve 10 I3 which is keyed to the shaft 2. The drum turns with respect to the shaft and the sleeve, the shaft being normally held against krotation by a worm gear. assembly at one end of the shaft. This assembly comprisesthe worm gear 'I4 and a worm 15 pinion I5, the latter being journalled in the casing section 3 with one end accessible for turning to wind up the spring to adjust its tension.- The .opposite ends of .the shaft 2 arejournalled in the casing sections 3 and 4, respectively, as shown. 20

The safety lock of my invention in the particular embodiment shown herein comprises a pawl I6 pivoted'at I1 in the drum'l and projectible through a slot I8 in the drum at a pointv in the circumference of the last convolution of the sp-iral groove 6. This convolution is located at the larger end of the drum and the pawl I6 is preferably disposed a little more than 180 from where the inner end of the cable is attached to the drum as shown in Fig. 2. The pawl is normally pressed 30 outwardly fro-1n the drum by a coiled spring I9 having one end seated in the drum and the other end seated in the pawl as shown.

The pawl `is mounted in a receivingchamber 20 provided in the drum. This chamber prefer- 35 ably opens through the side of the drum adjacent the cover plate 4 asshown in Fig. 2, whereby the pawl may be inserted in the drum and also whereby access may be had to the pawl Whenever de sired upon removal of the cover plate and the 40 drum cover 2 I.

The cable when Wound on the drum holds the pawl within the (chamber 2U, the portion of the pawl engaging the cable being grooved as shown to conform .to the groovein the drum. As the ,45 cable is unwound from the drum, the cable releases its restraining hold on the pawl before the inner end kof the cable reaches the cable outlet in the casing section 3. This occurs when the cable end is approximately V from this outlet. The 50 spring I9 then projects the free end of the pawl out of the drum for contact with an abutment or shoulder 22 in the casing section 3 to stop the rotation of the drum and relieve the connection be tween the cable andthe drum of strain or injury 55 whenv the cable is paid out to its fullest extent. This is important for the weight of the load or tool attached to the cable plus the pull of the operator on the cable'is sufficient to weaken the cable connection' especially when-repeated in the' use 60 of the balancer device. With this strain taken o the cable end and applied to the drum and its casing, respectively, the cable connection is not weakened and the cable can be pulled out without fear of straining or weakening the cable connection.

It will be noted in Fig. 2 that the drum case 3 is provided with an opening 23 in advance of the shoulder 22 whereby the pawl may drop into the opening to engage the shoulder and also whereby the pawl is accessible from the exterior of the drum case for pressing it back into its chamber 2S to permit winding the cable on the drum after the safety lock has operated.

As noted in Fig. l the inner or larger end of the drum is closely adjacent the casing section 3. The shoulder 22 is preferably fashioned as illustrated in Fig. 3 so that the shoulder is free of the larger end of the drum and is disposed opposite the terminal convolution of the groove.

The drum casing has means, indicated generally at 24, whereby the balancer may be suspended from an overhead support. The outer end of the cable is equipped with a suitable hook or equivalent means whereby a tool may be readily applied to and be removed from the cable.

The details of construction and arrangement of parts shown and described may be variously changed and modied without departing from the spirit and scope of my invention, except as pointed out in the annexed claims.

I claim as my invention:

1. In a balancer of the character described, a housing, a drum rotatably mounted in said housing, a cable windable on the drum, means for turning the drum in a direction to wind the cable thereon, said housing having an outlet opening for the cable, means connecting the inner end of the cable to the drum, said drum having an outwardly opening recess in its portion on which the cable winds and unwinds, said recess being located in advance of the connection of the inner end oi the cable with the drum in the direction of rotation of the drum to unwind the cable, an abutment on the housing, a pawl carried by the drum in said recess, said cable winding over the pawl and the recess for normally holding the pawl in the recess when the cable is wound on the drum, and means for projecting the pawl out of the recess when released by the cable for engaging the abutment to stop the rotation o1 the drum before the cable is completely unwound from the drum to relieve the cable connection with the drum of undue strain.

In a balancer of the character described, a housing, a drum rotatably mounted in said housing, a cable windable on the drum, said drum having a spiral groove to receive the cable, spring means for turning the drum in a direction to Wind the cable thereon, said housing having an outlet opening for the cable, means connecting the inner end of the cable to the drum at the terminal convolution of said groove, said drum having a recess opening outwardly through said groove in advance of the connection of the inner end oi the cable with the drum in the direction of rotation of the drum to unwind the cable, an abutment on the housing, a pawl carried by the drum in said recess, said cable Winding over' said pawl and said recess for normally holding the pawl in the recess when the cable is wound on the drum, said pawl having its outer end grooved to receive the cable when the cable winds over the pawl, and means for projecting the pawl outof the recess when released by the cable for engaging the abutment to stop the rotation of the drum before the cable is completely unwound from the drum to relieve the cable connection with the drum to undue strain.

3. In a balancer of the character described, a housing, a tapered drum rotatably mounted in said housing, a cable windable on the tapered portion of the drum, said tapered portion having a spiral groove thereon to receive the cable, a spiral spring for turning the drum in a cable winding direction, means for adjusting the tension of the spring, said cable extending out of the housing through an opening therein, means connecting the inner .end of the cable to the drum in the terminal convolution of the groove at the larger end of the drum, a pawl carried by the tapered portion of the drum at the terminal convolution oi said groove and projectible out of said groove into locking engagement with the housing to stop the rotation of the drum in an unwinding direction when the cable releases the pawl, said cable winding over said pawl when Wound on the drum for normally holding the pawl out of locking engagement with the housing, said pawl being located in advance of the cable connection with the drum in an unwinding direction so that the pawl will stop the rotation of the drum before the cable is completely unwound therefrom, and means for projecting the pawl out of the groove when released by the cable.

4. In a balancer of the character described, a housing, a drum rotatably mounted in said housing, a cable windable on the drum, spring means for turning the drum in a direction to wind the cable thereon, said housing having an outlet opening for the cable, means connecting the inner end of the cable to the drum, a locking element carried by the drum and projectible beyond the periphery of the drum into locking engagement with the housing to stop the rotation of the drum in an unwinding direction when the cable releases the locking element, said cable normally holding said element out of locking engagement with the housing when wound on the drum, said locking element being disposed to stop the rotation of the drum before the cable is completely unwound therefrom, and means for projecting the locking element into locking engagement with the housing when released by the cable.

5. In a balancer of the character described, a housing, a drum rotatably mounted in said housing, a cable windable on the drum, spring means for turning the drum in a direction to wind the cable thereon, said housing having an outlet opening for the cable, means connecting the inner end of the cable to the drum, a locking element carried by the cable receiving portion of the drum and projectible therefrom into locking engagement with the housing beyond the periphery of the drum to stopthe rotation of the drum in an unwinding direction when the cable releases the locking element, said cable winding over said element when wound on the drum for normally holding the eiement out of locking engagement with the housing, said locking element being located in advance of the cable connection with the drum in an unwinding direction so that the element will stop the rotation of the drum before the cable is completely unwound therefrom, and means for projecting the locking element into locking engagement with the housing when releasedby the cable.

FRITHIOF P. FORSS. 

